namespace tensorflow {

Operation::Operation(Node* n) : inputs_(GetInputs(n)), node_(n) {}

Output Operation::input(int32_t i) const {
  CHECK_NOTNULL(node_);
  CHECK_GE(i, 0);
  CHECK_LT(i, node_->num_inputs());
  // Handle the case where the input was unknown at the time this
  // Operation was constructed.
  if (inputs_[i].first == nullptr && inputs_[i].second == -1) {

  handle_data.set_is_set(true);
  {
    mutex_lock l(graph->mu);
    tensorflow::shape_inference::InferenceContext* ic =
        graph->refiner.GetContext(node);
    CHECK(ic != nullptr);
    CHECK_LT(output.index, ic->num_outputs());
    const auto* shapes_and_types =
        ic->output_handle_shapes_and_types(output.index);
    if (shapes_and_types == nullptr) return "";

    for (const auto& p : *shapes_and_types) {